Use of hydrogen peroxide for subsurface remediation: Microbial responses and their implications

Author

Fiorenza, Stephanie

Date

1992

Advisor

Ward, C. H.

Degree

Doctor of Philosophy

Abstract

Bioremediation uses microorganisms to degrade chemicals of interest and can be limited by mineral nutrients and terminal electron acceptors, especially oxygen. This research investigated in situ bioremediation with hydrogen peroxide (H$\sb2$O$\sb2$) as a supplemental oxygen source, added in increasing concentration, and addressed the microbial responses to H$\sb2$O$\sb2$. The microbial responses studied were changes in microbial numbers, population structure, degradative ability, and adaptation by induction of catalase and superoxide dismutase. Several assays were developed for this work.
Batch experiments, using microcosms of aquifer material from two sites, Traverse City, MI (TCM) and Granger, IN (GI), contaminated with gasoline, determined mineralization of $\sp{14}$C-toluene. Aquifer material treated with H$\sb2$O$\sb2$ in situ in GI mineralized more toluene than untreated contaminated material; when supplemented with H$\sb2$O$\sb2$, it had a greater rate of mineralization. These results indicated that subsurface microorganisms had adapted to the H$\sb2$O$\sb2$ applied in GI.
At a field demonstration in TCM, heterotrophs and hydrocarbon degraders declined in deep, uncontaminated subsurface cores and deep level cluster wells 7 feet and 31 feet from the H$\sb2$O$\sb2$ injection wells, demonstrating toxicity. Microbial numbers were elevated and soil catalase activity was induced in shallow, contaminated cores at 31 and 62 foot distances after the addition of H$\sb2$O$\sb2$, indicating adaptation.
Columns filled with slightly contaminated aquifer material from TCM were perfused with benzene, toluene, ethylbenzene, and o- and m- xylene (BTEX) and increasing concentrations of H$\sb2$O$\sb2$. Catalase and superoxide dismutase were induced, especially at the column inlets. Microbial numbers were higher at the column inlets. Abiotic H$\sb2$O$\sb2$ decomposition was observed in a sterile column; at a feed concentration of 500 mg/l, gas production impeded flow. The biologically active columns required increases in the BTEX concentration to eliminate plugging caused by oxygen gas evolution from catalase activity. The oxygen:BTEX mass ratio was 0.3 before H$\sb2$O$\sb2$ addition.
These results showed that subsurface microorganisms could, if a carbon source was available, adapt to a continuous input of H$\sb2$O$\sb2$. The low O:BTEX mass ratio and the requirement for an increase in BTEX when the H$\sb2$O$\sb2$ concentration was increased demonstrated that supplemental H$\sb2$O$\sb2$ was unnecessary in these column studies.